1. Field of the Invention
The present invention relates to a backlight assembly and a direct lighting type LCD (Liquid Crystal Display) apparatus, and more particularly to a backlight assembly for improving display quality by partially controlling brightness and a direct lighting type LCD apparatus employing the backlight assembly of the present invention.
2. Description of the Related Art
Information processing devices have been developed for improvements on their shapes, functions, and high data processing speed. In such information processing devices, information is processed in the form of electrical signals to be displayed on a display device such as an LCD apparatus.
LCD apparatuses generally have a lighter weight and a smaller size as compared with CRT (Cathode Ray Tube) type display devices, and have been developed to achieve full-color and high-resolution functions. In the LCD apparatuses, an arrangement of liquid crystal molecules is changed into a specific arrangement by applying a voltage to the liquid crystal molecules. The LCD apparatuses convert variations in optical properties of liquid crystal cells into variations in visual properties, thereby displaying images on an LCD apparatus. Generally, an LCD apparatus receives light from a backlight assembly disposed under an LCD panel and displays images on the LCD panel.
Backlight assemblies may be classified into those for direct lighting type LCD apparatuses and those for edge type LCD apparatuses based on the position of light sources. In a direct lighting type LCD apparatus, light is provided to an LCD panel from a plurality of light sources disposed under the LCD panel, so that the direct lighting type LCD apparatuses may provide higher brightness of images compared with the edge type LCD apparatuses.
FIG. 1 is a cross-sectional view showing a structure of a conventional direct lighting type LCD apparatus.
Referring to FIG. 1, the direct lighting type LCD apparatus 100 includes an LCD panel 110 for displaying an image and a backlight assembly 120 for supplying light to the LCD panel 110.
The backlight assembly 120 includes a plurality of lamps 121 for generating a first light, a diffusing plate 123 for diffusing the first light and generating a second light having uniform brightness distribution, and a lamp reflecting plate 122 for reflecting the first light to the diffusing plate 123. The lamps 121, lamp reflecting plate 122 and diffusing plate 123 are received in a receiving container.
The receiving container includes a bottom mold frame 124 and a bottom chassis 125 combined to each other using a hook. The bottom mold frame 124 has a quadrangle shape, and sidewalls of the bottom mold frame 124 are parallel to the longitudinal direction of the lamps 121 and inclined at a predetermined angle. The sidewalls of the bottom mold frame 124 are each provided with a step on which an edge portion of the diffusing plate 123 is placed. The bottom chassis 125 has a rectangular parallelepiped shape, and an upper surface of the bottom chassis 125 is open to provide a receiving space. The lamp reflecting plate 122 is received in the receiving space and the lamps 121 are disposed on the lamp reflecting plate 122.
A portion of the first light emitted from the lamps 121 is incident on the diffusing plate 123, and the remaining portion of the first light is reflected from the lamp reflecting plate 122 and supplied to the diffusing plate 123. As a result, the diffusing plate 123 emits the second light after diffusing the light directly from the lamps 121 and the reflected right from the lamp reflecting plate 122.
The direct lighting type LCD apparatus further includes an upper mold frame 130 disposed on the diffusing plate 123. The LCD panel 110 is disposed on the upper mold frame 130. A top chassis 140 is combined to the bottom chassis 125 to secure the LCD panel 110.
As shown in FIG. 1, the lamp reflecting plate 122 has a flat plate shape and the lamps 121 are disposed proximately on the lamp reflecting plate 122. When those of the lamps 121 disposed at the central area of the lamp reflecting plate 122 are referred as first lamps 121 a and those of the lamps 121 disposed at the end portions of the lamp reflecting plate 122 are referred as second lamps 121b, the first lamps 121a are each disposed between two adjacent lamps and the second lamps 121b are each disposed adjacent to only one lamp. As a result, the brightness at the end portions of the LCD panel 110 is lower than that at the central portion of the LCD panel 110 as a brightness distribution curve 150 shows in FIG. 1.
Accordingly, the direct lighting type LCD apparatus 100 has brightness distribution which is not uniform over the entire screen thereof, so that display quality of the direct lighting type LCD apparatus 100 is deteriorated.
Also, a vertical distance between the respective lamps 121 and the diffusion plate 123 has an identical distance d1, so that the brightness distribution of the direct lighting type LCD apparatus 100 may not be partially controlled.